Autodesk Storm and Sanitary Analysis offers users the ability to perform runoff calculations and hydraulic routing calculations in a single package. This combines the best of both worlds.
SSA’s hydraulic calculations are founded in the EPA SWMM calculations which performs the one-dimensional Saint Venant flow equations. The Saint Venant equations consist of the continuity and momentum equations for conduits and a volume continuity equation at nodes. What this means is culvert entrance and exit losses are computed not on the nodes themselves, but rather on the pipe ends.
Let’s dissect how this happens.
- Open the SSA Sample Culvert file. (C:\Program Files (x86)\Autodesk\SSA 2013\Samples\Culvert\Culvert.spf)
- Double Click on the Culvert Pipe shown in the image above. The Shape definition is described as a “Culvert”. In many cases, if you exported your Civil 3D Pipe network, the imported pipe may be just a “Pipe”.
- By selecting Culvert, the available properties of the conveyance link changes.
- The HDS-5 Culvert type and Culvert Entrance properties become available. Be sure to visit the Flow Properties section immediately below and properly set the Entrance and Entrance Losses.
The model is set for analysis.
Here is one tip when exporting your Civil 3D pipe network. If the Part Matching Default Settings on Export, set the upstream structure to Headwall, SSA imports that structure as a Junction, and sets the following downstream pipe to a Culvert.
One could conceivably use the Part Matching Customization Settings in SSA to match set a specific part family to a culvert, but that is a topic for another day.